1. Field of the Invention
The present invention relates to an information signal reproducing apparatus, and more particularly to an apparatus for reproducing an information signal together with additional information.
2. Description of Related Art
Digital recording and reproducing apparatuses for recording and reproducing video data and/or audio data, as digital data, on and from a magnetic tape, are known. As one of various formats for a digital VTR (video tape recorder) or VCR (video cassette recorder) of such a type for recording and reproducing video data as digital data, a format for recording and reproducing, together with the recording data, auxiliary data related to image data to be recorded (hereinafter, the auxiliary data being referred to as the system data) has been proposed by the HD-Digital VCR Conference. In this format, a recording date, tape position information, and the like are recorded on a magnetic tape, as the system data together with image data.
For example, system data indicative of a recording date is recorded on each of a subcode sector, a video sector and an audio sector of each track formed on a tape T shown in FIG. 1. The system data recorded on the video sector is recorded on a portion thereof indicated by xe2x80x9cVAUX DATAxe2x80x9d in FIG. 2, in units of one sync block (90 bytes). In addition, error correction check data for the video sector is recorded in the form of a product code composed of inner parity data and outer parity data, as shown in FIG. 2. FIG. 2 shows the manner in which data is recorded on the video sector of one track. The VAUX data is recorded on three sync blocks of sync block Nos. 19, 20 and 156, and the video data is recorded on 135 sync blocks of sync block Nos. 21 to 155.
On the subcode sector, only the system data is recorded. The subcode sector is composed of data in units of one sync block (12 bytes), as shown in FIG. 3. In addition, error correction check data for the subcode sector is recorded only as inner parity data, as shown in FIG. 3. FIG. 3 shows the manner in which data is recorded on the subcode sector of one track. The data recorded on the subcode sector is composed of 12 sync blocks of sync block Nos. 0 to 11.
In a search mode in which the magnetic tape on which data has been recorded as described above travels at a speed which is n times (n greater than 1) a speed used at the time of recording the data, the entire area of one track cannot be traced by a magnetic head, as indicated by a broken line in FIG. 4. In addition, when the tape traveling speed is increased to a higher speed, the possibility that the VAUX data, which has a large one-sync block length, can be reproduced by one tracing operation becomes lower than the possibility that the subcode data, which has a small one-sync block length, can be reproduced by one tracing operation. On the other hand, since the VAUX data is subjected to error correction using the inner parity data and the outer parity data, the VAUX data does not easily cause erroneous detection and uncorrectable error of the system data, as compared with the subcode data, which has only the inner parity data.
A known function using date data as the system data recorded as described above, is a date search function.
When a date search is to be performed, an operation of detecting a change point of recording dates has the following problems. More specifically, when system data is to be detected, in general, the system data is repeatedly reproduced a plurality of times to prevent erroneous detection. When the contents of the repeatedly reproduced system data coincide with each other, the contents are determined/confirmed. Therefore, in a case where recording-date data is recorded on or reproduced from both the VAUX data and the subcode data, since an error of the VAUX data is corrected using the inner parity data and the outer parity data, and an error of the subcode data is corrected using only the inner parity data, the number of times of repeated reading operations of the subcode must be made larger than the number of times of repeated reading operations of the VAUX data in order to prevent erroneous detection.
In addition, as the traveling speed of the magnetic tape increases, the magnetic head cannot completely trace each track of the magnetic tape, as indicated by the broken line in FIG. 4. In this case, when the VAUX data, in which one sync block is composed of 90 bytes, is compared with the subcode data, in which one sync block is composed of 12 bytes, the possibility that the subcode data, in which one sync block has a smaller amount of data, can be detected is higher than the possibility that the VAUX data can be detected, even if the traveling speed of the magnetic tape becomes sufficiently high as to make it impossible to completely trace each track. In other words, the tape traveling speed at which the subcode data can be detected is generally higher than the tape traveling speed at which the VAUX data can be detected.
Therefore, when recording-date data is to be detected from the VAUX data or the subcode data, it is necessary to set the number of times of repeated reading operations to that of the subcode data, and it is necessary to set the tape traveling speed to a speed at which the VAUX data can be detected. As a result, a detection speed of the recording-date data becomes low.
It is an object of the present invention to overcome the problems described above.
It is another object of the present invention to rapidly detect additional information recorded on a recording medium.
To attain the above objects, in accordance with one aspect of the invention, there is provided a reproducing apparatus, comprising reproducing means for reproducing main data and subdata related to the main data from a recording medium, the subdata being recorded on a first area and a second area of the recording medium, and determining means for detecting the subdata reproduced by the reproducing means, where the determining means determines/confirms the value of the detected subdata when (i) subdata having the same value has been detected from the first area n times (n being an integer not less than 2), or (ii) when subdata having the same value has been detected from the second area m times (m being an integer not less than 2).
It is still another object of the present invention to make it possible to perform excellent searching.
The above and other objects and features of the present invention will become apparent from the following detailed description of a preferred embodiment thereof taken in connection with the accompanying drawings.